In case you were curious, here is what an alien sees before he/she/it goes to sleep.

NASA’s Curiosity Mars rover captured the above image on April 15, and it’s being described as the first sunset observed in color by the spacecraft.

The photos were taken last month, but they were just sent back to Earth last week.

While Mars may appear red, the sunset is actually blue, and the Jet Propulsion Laboratory explains why this is possible:

Dust in the Martian atmosphere has fine particles that permit blue light to penetrate the atmosphere more efficiently than longer-wavelength colors. That causes the blue colors in the mixed light coming from the sun to stay closer to sun’s part of the sky, compared to the wider scattering of yellow and red colors. The effect is most pronounced near sunset, when light from the sun passes through a longer path in the atmosphere than it does at mid-day.

Curiosity first landed on Mars’s Gale Crater in August 2012 with a mission of determining whether or not Mars is or ever was habitable by life forms.

Here’s an animated GIF of the sunset, which uses a series of photos takes over a period of about 6 minutes, 51 seconds. The sight apprently inspired the rover to recite some lines from T.S. Eliot’s “The Love Song of J. Alfred Prufrock” on its Twitter account.

Via Washington Post:

NASA announced evidence on Thursday that Jupiter's largest moon, Ganymede, has a saltwater ocean under its icy surface. The ocean seems to have more water than all the water on Earth's surface, according to new Hubble observations.

Scientists estimate that the ocean is 60 miles thick, which is about 10 times deeper than Earth's oceans. But unlike our salty waters, Ganymede's ocean is buried under 95 miles of ice.

The tool is a motorized, wire-bristle brush designed to prepare selected rock surfaces for enhanced inspection by the rover's science instruments. It is built into the turret at the end of the rover's arm. In particular, the Alpha Particle X-ray Spectrometer and the Mars Hand Lens Imager, which share the turret with the brush and the rover's hammering drill, can gain information after dust removal that would not be accessible from a dust-blanketed rock.